Conventionally, there have been exclusively used the cargo vessels which are adapted to the configurations, weights and properties of the cargoes to be carried. Thus, since one cargo vessel has been unable to carry all the kinds of cargoes, many kind of cargo vessel must be constructed corresponding to the application.
In general, a cargo vessel has a multi-story construction. In some of the vessels, each of the decks is stationary and in other cargo vessels, it is wholly vertically movable so that it must be adjusted in height based on the greatest height of the cargoes to be received in the corresponding hold. A disadvantage of such cargo vessels is that if the hold receives various cargoes different in height, the vacant or dead space will exist above the lower cargoes to cause deterioration of the loading capacity.
In case a cereal carrying vessel receives and carries cereals, they cause the vessel to be out of balance during its voyage due to their movement toward the lower side of the vessel when it tilts on the wave. An ore vessel must be provided at both sides with large ballast tanks to prevent the vessel from being out of balance, which causes deterioration of the loading capacity.